Fiber optics are one of the most important new media for transmitting information. Fiber optics are capable of carrying enormous quantities of voice, data and video traffic on light impulses over hair-thin glass fibers. Fiber optics transmit more information and data over a shorter period of time than circuit-transmission media. For example, optical signals may be transmitted over fiber optics with losses of less than 0.1 dB/krn. In sharp contrast, data generally is transmitted over a pair of twisted copper wires with losses of up to 50 dB/km. The capabilities of fiber optics have fundamentally changed communications.
The fiber optics industry has exploded as the Internet and telecommunication field have created a skyrocketing demand for broadband, high-speed pipe lines to carry data. Long-span fiber optic networks of 100 kilometers or more carry bandwidth ranging from 40 to 50 giga bites per second. Similarly, high-speed fiber optics are capable of connecting wide-area networks of approximately 200 kilometers. Also, fiber optics may connect metropolitan networks of 500 meters to 2 kilometers, such as connecting one building to another building. The largest growth area for high-speed fiber optics, however, is connecting distances of less than 300 meters. In this sub-300 meter or short-distance market, fiber optics are used for a wide variety of purposes, including connecting computers within a room and linking routers, switches and transport equipment.
While significant progress has been made in the area of fiber optics, more wide-spread use is dependent upon the availability of a low cost, easy-to-use and efficient (i.e., low loss of light) optical transmitter and receiver module to link fiber optics to various electronic devices and components such as computers and routers. A critical aspect of such a module is the accurate alignment and attachment of the individual optical fibers to the electronic devices that transmit and receive light streams to and from the optical fibers. These electronic devices, known as optoelectronic devices, use optical and electronic technology or optoelectronics to convert electrical signals into optical radiation or light and transmit the radiation into optical fibers. Other optoelectronic devices receive optical radiation from optical fibers and convert it into electrical signals for processing. Accurate alignment and attachment of the individual optical fibers to the optoelectronic devices is essential to achieving a good and efficient optical connection, one that produces a low loss of light at the interface between the optical fibers and the optoelectronic devices.
A known method for precisely coupling optical fibers to optoelectronic devices is active alignment. Specifically, a photo-detector is placed at one end of an optical fiber, and an optoelectronic device, such as a vertical cavity surface emitting laser, is placed near the other end of the optical fiber. After turning on the laser, the optical fiber is manipulated manually around the light-emitting surface of the laser until the photo-detector detects the maximum amount of optical radiation as indicated by an output electrical signal. Similarly, a photo-detector can be actively coupled to an optical fiber by transmitting laser light into one end of an optical fiber and manually adjusting the position of the other end of the optical fiber relative to the photo-detector until the detector receives the maximum amount of optical radiation.
Actively aligning an array of optical fibers to an array of optoelectronic devices is not practical because the dimensions of an optoelectronic device and the cross-section of an optical fiber are small and multiple dimensions of rotation and translation motion must be controlled. The active alignment process to connect even a single optical fiber strand to an optoelectronic device is usually time-consuming and requires knowledge, skill and expertise. The active alignment process is particularly laborious and time-intensive when a number of optical fibers must be individually aligned to an array of optoelectronic devices. This process requires a variety of relatively complex and costly components that significantly increase the fabrication costs to produce precisely aligned optical devices. Moreover, during the active alignment process, optoelectronic devices emit a significant amount of optical power and energy. The heat generated by the devices can produce thermal strain that may cause the optical fibers and the optoelectronic devices to be misaligned.
Various passive alignment techniques have been developed, such as the use of guide pins and holes, to attempt to provide fast, easy and simultaneous alignment and attachment of an array of optical fibers to optoelectronic devices. Passive alignment typically indicates a technique for aligning a laser and an optical fiber that does not require the laser to be turned on during the alignment process; whereas an “active” technique requires the laser to be turned on. However, these passive alignment techniques often do not provide a precision coupling of the optical fibers to optoelectronic devices.
Accordingly, there is a need in the art to provide a method and apparatus for precise, fast and easy alignment and attachment of optical fibers to optoelectronic devices, which may be mounted on a circuit board. In addition, there is a need in the art to provide an inexpensive method and apparatus for aligning and attaching optical fibers to optoelectronic devices so that the method and apparatus are suitable for mass production. Finally, there is a need in the art for a small apparatus coupling optical fibers to optoelectronic devices so that the apparatus can easily be mounted on a circuit board.